Fuel injection refers to a system for admitting fuel into an internal combustion engine, and has become the primary fuel delivery system used in automotive engines, having replaced carburetors. The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake air accelerated through a Venturi tube to draw the fuel into the airstream. Modern fuel injection systems are designed specifically for the type of fuel being used. Some systems are designed for multiple grades of fuel (using sensors to adapt the tuning for the fuel currently used). Most fuel injection systems are for gasoline or diesel applications.
Benefits of fuel injection include smoother and more consistent transient throttle response, such as during quick throttle transitions, easier cold starting, more accurate adjustment to account for extremes of ambient temperatures and changes in air pressure, more stable idling, decreased maintenance needs, and better fuel efficiency. Fuel injection also dispenses with the need for a separate mechanical choke, which on carburetor-equipped vehicles must be adjusted as the engine warms up to normal temperature. Fuel injection systems are also able to operate normally regardless of orientation, whereas carburetors with floats are not able to operate upside down or in zero gravity, such as encountered on airplanes. Fuel injection generally increases engine fuel efficiency. Exhaust emissions are cleaner because the more precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine, and because exhaust cleanup devices such as the catalytic converter can be optimized to operate more efficiently since the exhaust is of consistent and predictable composition.
Gasoline direct injection (GDI) is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines, where the gasoline is highly pressurized, and injected via a common rail fuel line directly into the combustion chamber of each cylinder as shown in FIG. 1B, as opposed to conventional multi-point fuel injection that injects fuel into the intake tract, or cylinder port (FIG. 1A). Directly injecting fuel into the combustion chamber requires high pressure injection whereas low pressure is used injecting into the intake tract or cylinder port.
A problem encountered with fuel injection systems is the buildup of carbon deposits on the inlet side (top) of the intake valves. The deposits create turbulence and can restrict airflow into the cylinders causing performance and driveability problems including hesitation, stumbling, misfiring, and hard starting. The thicker the carbon deposit buildup on the valves, the worse the driveability problems. While many fuels have additives to clean intake valves these additives are ineffective for GDI based engines, since GDI sprays fuel directly into the combustion chamber, as shown in FIG. 1B, so the fuel completely bypasses the intake valves. Consequently, detergents and cleaners that are added to gasoline to prevent intake valve deposits from forming in port fuel injection engines never have a chance to do their job in a GDI engine. The inlet side of the intake valves are never in direct contact with the fuel so the detergents cannot wash away the deposits. Because of this, fuel detergent additives that are either in gasoline from the refinery or are added to the fuel tank have almost no effect on preventing or removing intake valve deposits in GDI engines. The additives work in regular port fuel injected engines, but not GDI engines.
Thus, there exists a need for a method and system for evaluating the delivery and effectiveness of engine performance chemicals and products for reducing intake valve deposits for gasoline direct injection and port fuel injection engines.